Ammonium uranate heated to redness yields pure U308, which serves as a raw material for uranium compounds.
It is manufactured by heating pitchblende with lime, treating the resulting calcium uranate with dilute sulphuric acid, and adding sodium carbonate in excess.
Sodium uranate, Na2U207, is used as a pigment for painting on glass and porcelain under the name of uranium yellow.
The filtrate, on being boiled down, yields a second crop of uranate.
The precipitate, after having been collected and washed, is digested with a warm concentrated solution of ammonium carbonate, which dissolves the uranium as a yellow solution of ammonium uranate, while the hydrated oxide of iron, the alumina, &c., remain.
These are filtered off hot, and the filtrate is allowed to cool, when crystals of the uranate separate out.
This uranate when ignited in a platinum crucible leaves a green oxide of the composition U308, i.e.